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Radio frequency modulation of semiconductor laser as an improvement method of noise performance of scanning probe microscopy position sensitive detectors

Skwierczyński J. M., Maloziec G., Kopiec D., Nieradka K., Radojewski J., Gotszalk T. P.

Optica Applicata

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2011

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Vol. 41, nr 2

323--331

EN

An experimental investigation was made on use of radio frequency (RF) modulation of a semiconductor laser in order to improve the noise performance of the scanning probe micros-copy cantilever position sensitive detector. High resolution measurements of the cantilever displacement are limited by optical power intensity noise of the laser diode. In general, the intensity noise is formed by mode hopping or mode partition phenomena in the laser multimode and single mode regimes. Furthermore, the measurements are disturbed by an optical feedback, which is caused when light is scattered back into the laser cavity. In order to reduce the laser intensity noise and the optical feedback, we developed a precise laser automatic power control (APC) driver with RF modulation of the DC diode bias current. Our experiments showed that the spectral noise density of the developed scanning probe microscopy detection system was 3 times smaller than the noise density of the system without RF operating current modulation. In a low power operation, near the diode threshold current, the laser mode partition noise is dominating and it can be reduced by adjusting the modulation current frequency to 300 MHz. In this paper, the architecture of the designed system will be presented. We will also discuss the results of noise performance investigations of the scanning probe microscopy position sensitive detectors applied in precise surface measurements.

2

Układ lock-in z cyfrową syntezą częstotliwości w technice FPGA

Szecówka P. M., Zając M., Gotszalk T. P., Zielony M., Jóźwiak G., Stania R.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 10

120-122

PL

Opisano własną konstrukcję komputerowo sterowanego układu lock-in. Kluczowe elementy - detektor fazy i generator częstotliwości odniesienia wykonano w technice cyfrowej, w oparciu o język VHDL i programowalne układy logiczne FPGA. Przebiegi sinusoidalne generowano za pomocą rozwinięcia w szereg Maclaurina. Pokazano, że przy wydłużonym czasie zbierania próbek i uśrednianiu wyników można przeprowadzić analizę rezonatora 32 kHz pomimo zastosowania przetworników A/C i C/A o niewiele większych częstotliwościach próbkowania.

EN

In-house developed, computer-controlled lock-in system is presented. Crucial elements - phase detector and direct digital synthesizer were based on digital technique (VHDL and FPGA). Sine signals are generated in real time by Maclaurin series approximation. It was shown that for extended time of samples collection, resonant frequency of 32 kHz oscillator may be measured, in spite of applying A/D and D/A converter working with sampling rate only silghtly exceeding the measured frequency.

3

Uncertainty of atomic force microscopy measurements

Gotszalk T.P., Janus P., Marendziak A., Szeloch R.F.

Optica Applicata

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2007

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Vol. 37, nr 4

397-403

EN

We consider the problem of uncertainty in geometrically linear measurements in scanning probe microscopy (SPM) represented by atomic force microscopy (AFM). The uncertainties under consideration are associated both with quantum phenomena in the space cantilever tip--sample surfaces and with effects of dynamic behavior of electronic and optic measurement and control systems. In our experiment, we have analyzed uncertainty of calibrated atomic force microscopy (C-AFM) measurement in two dimensions. Uncertainty of measurements has been estimated according to GUM procedure.

4

Thermal characterization of copper thin films made by means of sputtering

Szeloch R. F., Posadkowski W. M., Gotszalk T. P., Janus P., Kowaliw T.

Materials Science

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2003

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Vol. 21, No. 3

339-343

EN

Copper thin films have been deposited onto Corning glass substrates by means of two kinds of DC magnetron sputtering. The goal of this research was to study differences in thermal characteristics of both kinds of the films. The differences between these layers originate from the technological processes; one of them employs an inert gas -- argon -- in the vacuum chamber, and the other is the so-called "pure" self-sputtering. Thermal characterization of the layers was performed using the scanning thermal microscopy (SThM) as well as a far field thermographical system.

5

Application of electrostatic force microscopy in nanosystem diagnostics

Gotszalk T. P., Grabiec P., Rangelow I. W.

Materials Science

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2003

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Vol. 21, No. 3

333-338

EN

The current state of art of electrostatic force microscopy is described in the paper. The principle of electrostatic force operation enabling one to analyse local voltage distribution and capacitance is pre-sented. The design and properties of electrostatic force microscopy microprobes are discussed. The application and manufacturing process of piezoresistive cantilevers with conductive tips and of silicon beams with metallic probe are presented. In order to show the capabilities of electrostatic force micros-copy methods of investigations of local voltage distribution on surfaces of microelectronic integrated circuits (IC) are described. Improvements of electrostatic force microscopy and of other electrical meth-ods based on scanning probe microscopy confirm an increasing interest in electrical probing at the nanometre scale.

6

Mikroskopia sił atomowych "Shear force" z interferencyjną detekcją ostrza skanującego

Sikora A., Sankowska A., Gotszalk T. P., Radojewski J., Szeloch R. F.

Elektronizacja : podzespoły i zastosowania elektroniki

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2002

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nr 9

11-12